Wireless communication devices, such as but not limited to wireless telephones that communicate using Code Division Multiple Access (CDMA) spread spectrum modulation techniques, communicate over the air with system infrastructure using wireless telephone over-the-air communication protocols, e.g., the CDMA protocols known as IS-95A and IS-2000. The system infrastructure, which can include base stations (BTS), base station controllers (BSC), and other components, connects the wireless telephone to another communication device, such as a through land line or another wireless communication system.
In the case of CDMA, voice data is sent over the air in packets that are collected by the infrastructure and assembled into a voice stream, transparently to the speakers who are talking to each other. As might be expected, the over-the-air protocol is tailored to optimize wireless communication. For instance, to maximize over-the-air capacity, the over-the-air protocol contains a minimum of signalling information, and the size of a voice data packet is relatively small.
With the growth of the Internet, computer-to-computer communication using Internet Protocols (IP) has become ubiquitous. Furthermore, it has become desirable not only to facilitate computer data communication using IP, but to facilitate voice communication using IP as well. As but one advantage afforded by using IP in a telephony infrastructure, much hardware such as switches can be eliminated, and existing computers and software can be used instead, reducing cost. To this end, so-called voice over IP (VOIP) has been introduced.
To support VOIP, a communication device must have, among other requirements, an IP address, so that the IP-based infrastructure knows where to send data and voice packets intended for the device. Typically, the IP address for a wireless device is not static, but rather one is assigned to a device upon power-up by a local network carrier from a pool of IP addresses assigned to the carrier. According to current protocol, the device registers its temporary IP address by sending a registration message through the Internet to an SIP server that is not necessarily associated with the local network carrier.
The present invention understands that for several reasons, many local networks assign internal IP addresses to their devices, with the internal IP addresses being routable only within the local network and not outside the system through the rest of the Internet. This might be done, e.g., because a system might be allocated a block that contains only a limited number of routable IP addresses, whereas it can define an almost unlimited number of internal IP addresses to allocate to its various devices for internal communication-only purposes.
To preserve system security by preventing non-system devices from learning about the local network's internal topology, which might otherwise be possible, and to provide a means by which a wireless communication device can communicate outside the local network (as is typically required to complete a VOIP communication path through the Internet), many local networks that employ internal-only addresses include an interface to the Internet referred to as a network access translation (NAT) component. Among other things, the NAT translates a device's internal IP address, sometimes referred to herein as a “private” IP address, to an Internet-routable IP address, sometimes referred to herein as a “public” IP address. It is to a device's public IP address that IP packets must be sent, and from a device's public IP address from which IP packets must appear to have originated.
However, as critically observed by the present invention, it is the public IP address—the one that is assigned by the NAT and that consequently is unknown to the device—that a device must register with the external SIP server. The present invention accordingly recognizes that a method must be provided for wireless communication devices in local networks such as described above to register their public, NAT-assigned IP addresses with an SIP server that is external to the local network. Moreover, the present invention understands that in preferred non-limiting embodiments the registration procedure should not necessarily require an additional proxy server located at the NAT interface, since this would be expensive and/or impractical in many cases and potentially not under the user's control.